The present invention relates to shielding undesirable background electromagnetic radiation from background limited radiation detectors. Such shielding is particularly applicable to infrared detectors and systems. However, shields in accordance with the present invention are equally applicable to other background limited detector systems in which it is desirable to shield background radiation in the spectral or electromagnetic energy band of the system detectors.
With background limited infrared detectors, individual detector sensitivity or figure of merit is generally recognized to be inversely proportional to the square root of background radiation. Therefore, it is desirable to limit detector background so that each detector in an array sees only the applicable optics of the infrared system.
Lowering background by shielding at the optics is cumbersome and adds weight or complexity to the system. Accordingly, shielding at the detector has long been recognized as an effective and workable approach to limiting background radiation. One such approach is described in U.S. Pat. No. 3,963,926, S. R. Borrello, "Detector Cold Shield" (hereinafter Borrello); however, as is further explained below, such cold shields have limited effectiveness in high density arrays and in mosaic arrays. Arrays of this nature, which are highly desirable in modern infrared systems, have not previously been adequately shielded from background radiation.